/*
 * Copyright 2012-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package lodsve.core.condition;

import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.util.ClassUtils;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;

/**
 * {@link Condition} that checks for the presence or absence of specific classes.
 *
 * @author Phillip Webb
 * @see ConditionalOnClass
 * @see ConditionalOnMissingClass
 */
@Order(Ordered.HIGHEST_PRECEDENCE)
class OnClassCondition extends SpringBootCondition {

    @Override
    public ConditionOutcome getMatchOutcome(ConditionContext context,
                                            AnnotatedTypeMetadata metadata) {

        StringBuilder matchMessage = new StringBuilder();

        MultiValueMap<String, Object> onClasses = getAttributes(metadata,
                ConditionalOnClass.class);
        if (onClasses != null) {
            List<String> missing = getMatchingClasses(onClasses, MatchType.MISSING,
                    context);
            if (!missing.isEmpty()) {
                return ConditionOutcome
                        .noMatch("required @ConditionalOnClass classes not found: "
                                + StringUtils.collectionToCommaDelimitedString(missing));
            }
            matchMessage.append("@ConditionalOnClass classes found: ")
                    .append(StringUtils.collectionToCommaDelimitedString(
                            getMatchingClasses(onClasses, MatchType.PRESENT, context)));
        }

        MultiValueMap<String, Object> onMissingClasses = getAttributes(metadata,
                ConditionalOnMissingClass.class);
        if (onMissingClasses != null) {
            List<String> present = getMatchingClasses(onMissingClasses, MatchType.PRESENT,
                    context);
            if (!present.isEmpty()) {
                return ConditionOutcome
                        .noMatch("required @ConditionalOnMissing classes found: "
                                + StringUtils.collectionToCommaDelimitedString(present));
            }
            matchMessage.append(matchMessage.length() == 0 ? "" : " ");
            matchMessage.append("@ConditionalOnMissing classes not found: ")
                    .append(StringUtils.collectionToCommaDelimitedString(
                            getMatchingClasses(onMissingClasses, MatchType.MISSING,
                                    context)));
        }

        return ConditionOutcome.match(matchMessage.toString());
    }

    private MultiValueMap<String, Object> getAttributes(AnnotatedTypeMetadata metadata,
                                                        Class<?> annotationType) {
        return metadata.getAllAnnotationAttributes(annotationType.getName(), true);
    }

    private List<String> getMatchingClasses(MultiValueMap<String, Object> attributes,
                                            MatchType matchType, ConditionContext context) {
        List<String> matches = new LinkedList<String>();
        addAll(matches, attributes.get("value"));
        addAll(matches, attributes.get("name"));
        Iterator<String> iterator = matches.iterator();
        while (iterator.hasNext()) {
            if (!matchType.matches(iterator.next(), context)) {
                iterator.remove();
            }
        }
        return matches;
    }

    private void addAll(List<String> list, List<Object> itemsToAdd) {
        if (itemsToAdd != null) {
            for (Object item : itemsToAdd) {
                Collections.addAll(list, (String[]) item);
            }
        }
    }

    private enum MatchType {

        PRESENT {
            @Override
            public boolean matches(String className, ConditionContext context) {
                return ClassUtils.isPresent(className, context.getClassLoader());
            }
        },

        MISSING {
            @Override
            public boolean matches(String className, ConditionContext context) {
                return !ClassUtils.isPresent(className, context.getClassLoader());
            }
        };

        public abstract boolean matches(String className, ConditionContext context);

    }

}
